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Block 6 - week 5 > Opportunistic Mycoses - Kozel > Flashcards

Opportunistic Mycoses - Kozel Flashcards

1
Q

Name some opportunistic mycoses.

A
  1. candidiasis
  2. aspergillosis
  3. mucormucosis
  4. cryptococcosis
  5. pneumocystosis
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2
Q

What is a mycosis?

A

A fungal infection.

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3
Q

Describe the Candida spp.

A
  1. C. albicans is the most common species
  2. these are primarily yeasts but also are pseudohyphae and true hyphae producers
  3. form germ tubes - which are hypha emerging form a yeast-like structure
  4. normal commensal in entire GI tract, female GU tract and skin
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4
Q

Name some other Cadida species.

A
  1. C. glabrata
  2. C. parapsilosis
  3. C. tropicalis
  4. C. luitaniae
  5. C. dublinensis
  6. C. krusei
  7. C. guilliermondii
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5
Q

Describe Candidiasis.

A
  1. most infections are endogenous - normal commensal that opportunistically causes infection
  2. infections include: mucous membrane, cutaneous candidiasis syndromes, deep organ infections
  3. is a major nosocomial infection - 3rd most common blood stream infection that adds $40,000 to cost of care
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6
Q

What types of mucous membrane infections does candidiasis include?

A
  1. Thrush - in mouth
  2. Candida esophagitis - often seen in AIDS
  3. Vaginitis - 75% of normal women have at least one episode
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7
Q

What types of deep organ involvement is seen in candidiasis?

A
  1. CNS
  2. Lungs -Pneumonia
  3. Bone and joints
  4. Urinary tract
  5. Abdominal infection
  6. Hematogenous disseminated candidiasis - an invasive form, most severe of deep organ involvement
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8
Q

What are the general risk factors for getting Invasive Candidiasis?

A
  1. hematologic malignancy
  2. neutropenia
  3. GI surgery
  4. premature infants
  5. elderly patients - over 70 years of age
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9
Q

What are the specific risk factors for getting Invasive Candidiasis?

A
  1. time spent in ICU
  2. central venous catheterization
  3. colonization at multiple sites
  4. number of antibiotics given
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10
Q

How is Candidiasis diagnosed?

A
  1. direct examination - scrapings of mucosal or cutaneous lesions are put on slide, KOH added to dissolve tissues, look for budding, yeast-like forms and pseudohyphae
  2. Cultures - can be grown from tissue scrapings or from body fluids. Blood can be used but is only 50% positive in invasive disease
  3. confirmation of diagnosis - germ tube formation when grown on serum
  4. mediums used for growth - standard mycologic media, selective chromogenic medium such as CHROMagar candida (different species are different colors)
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11
Q

How is oral thrush treated?

A
  1. topical - nystatin, clotrimazole
  2. oral systemic therapy - fluconazole or other azole
  3. prophylatic fluconazole in AIDS
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12
Q

How is Candida Esophagitis treated?

A
  1. topical therapy usually fails

2. oral systemic therapy with fluconazole works

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13
Q

How is Vaginitis caused by Candida treated?

A

If uncomplicated then can be treated by OTC azoles or oral azoles.

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14
Q

How is recurrent Candida Vaginitis treated?

A
  1. if possible - remove or treat causal factors such as HIV, uncontrolled diabetes, antibacterials, hormone replacement therapy
  2. induction course of azole followed by long-term maintenance regimen
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15
Q

How is deep-seated or invasive Candidiasis treated?

A
  1. Prevention - avoid broad spectrum antibiotics, meticulous catheter care, rigorous infection control
  2. Remove source of infection - drain abcesses, remove or change vascular catheter
  3. Antifungal agents
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16
Q

What type of anti-fungal agents are used to treat invasive Candidiasis?

A
  1. approach varies with site of infection and patient status such as neutropenia
  2. Polyene - amphotericin B or liposomal amphotericin B
  3. Triazole - primarilly fluconazole
  4. Echinocandin - primarily Caspofungin
17
Q

Name 3 types of anti-fungals that can be used to treat invasive Candidiasis.

A
  1. amphotericin B
  2. fluconazole
  3. caspofungin
18
Q

Describe the Aspergillus spp.

A
  1. form branched, septate hyphae
  2. form conidial heads with spheric conidia
  3. ubiquitous in air, soil and decaying vegetation
  4. worldwide distribution
    5 an emerging pathogen that is difficult to diagnose and treat
19
Q

Name some Aspergillus spp.

A

There are 19 disease-producing species. Following are some pathogens in order of how common they are.

  1. A. fumigatus - most common invasive species
  2. A. flavus
  3. A. niger
  4. A. terreus
20
Q

What types of diseases does Aspergillosis include?

A
  1. Allergic bronchopulmonary aspergillosis - a Th-2 type response
  2. Aspergilloma - fungus balls of lung formed by mass of hyphae in pre-existing cavities of lung
  3. Invasive syndromes
  4. Toxemia - caused by aflatoxin
21
Q

Describe the invasive syndrome of Aspergillosis.

A
  1. begins in lungs following inhalation of conidia
  2. fungi then invades blood vessels - angioinvasive
  3. associated with immunosuppression such as neutropenia, organ transplant, stem cell transplant or bone marrow transplant patients, corticosteroid use or other immunosuppressive therapies
22
Q

What are the two clinical forms of invasive Aspergillosis?

A
  1. invasive pulmonary aspergillosis

2. disseminated infection - extremely high mortality

23
Q

How is Aspergillosis diagnosed?

A
  1. typically requires tissue biopsy - sometimes too risky in immunocompromised pt
  2. Histopath - look for septate hyphae with acute-angle branching. Special stains - gomori methenamine silver, PAS.
  3. Culture - biopsy sample easy to culture, look for above morphology to identify Aspergillus, speciation is harder.
  4. blood cultures are rarely positive and culture from non-sterile site is difficult to interpret due to contamination
  5. radiology may be useful for invasive pulmonary infection
  6. Biomarkers such as B-glucan (nonspecific fungal marker) or galactomannan often very useful
24
Q

Is blood culture a diagnostic tool for diagnosis of Aspergillosis?

A

No, blood cultures are routinely negative even with invasive Aspergillosis.

25
Q

How is Aspergillosis prevented?

A
  1. pt isolation
  2. HEPA filter use
  3. positive pressure
  4. pozaconazole prophylaxis for very high risk pt’s
26
Q

How is Aspergillosis treated?

A
  1. voriconazole - primary therapy

2. alternatives - Amphotericin B, other triazoles, Echinocandins

27
Q

Describe the Mucorales spp.

A
  1. morphology includes coenocytic hyphae - few septae, multinucleate
  2. morphology includes - saclike fruiting structure (sporania) with internal spores called sprangiospores
  3. ubiquitous, found in decaying organic substrates such as bread, fruits, vegetable matter and soil
  4. infection is rare
  5. infection by inhalation, cutaneous or percutaneous inoculation of spores
28
Q

What genera of Mucorales cause disease?

A

In order of % of cases

  1. Rhizopus
  2. Mucor
  3. Cunninghamalia
  4. Absidia
29
Q

Describe the pathology of Mucorales infection.

A
  1. causes Mucormycosis
  2. fungi are angiovasive causes necrosis of vessel walls
  3. causes pulmonary infection, cutaneous infection, disseminated mucormycosis, and rhinocerebral disease (associated with diabetes mellitus)
30
Q

What are the risk factors for Mucorales infection?

A
  1. diabetes or metabolic acidosis
  2. neutropenia
  3. solid organ/hematopoitec stem cell transplant
  4. Chelation (Deferoxamine) therapy to remove excess iron - fungus uses deferoxamine for nutritional growth
31
Q

How is mucormycosis diagnosed?

A
  1. Take sample by biopsy or swab (blood cultures rarely pos.)
  2. Histopath - look for broad, empty, thin-walled mostly aseptate hyphae in sample
  3. Cuture - easy to culture, diagnose based on morphology, speciation can be done based on shape of the sporangium and location of sporangiospores but not easy
  4. tests for B-glucan or galactomannan are negative
  5. differentiation from other fungi is important because azoles do not work on mucorales spp
32
Q

How is Mucorales infection treated?

A
  1. reverse underlying condition, surgical resection
  2. amphotericin B is drug of choice
  3. resistant to many antifungals - ketoconazole, fluconazole, vorizonazole, flucytosine, and echinocandins
  4. overall has poor prognosis

Block 6 - week 5 (8 decks)

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